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29 lines
821 B
29 lines
821 B
var isStr = require('./isStr'); |
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var strToBytes = require('./strToBytes'); |
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var TABLE = []; |
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for (var n = 0; n < 256; n++) { |
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var c = n; |
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for (var k = 0; k < 8; k++) { |
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if (c & 1) { |
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c = 0xedb88320 ^ (c >>> 1); |
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} else { |
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c = c >>> 1; |
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} |
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} |
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TABLE[n] = c >>> 0; |
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} |
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if (typeof Int32Array !== 'undefined') TABLE = new Int32Array(TABLE); |
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exports = function(input, previous) { |
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return exports.signed(input, previous) >>> 0; |
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}; |
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exports.signed = function(input, previous) { |
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if (isStr(input)) input = strToBytes(input); |
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var crc = previous === 0 ? 0 : ~~previous ^ -1; |
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for (var i = 0, len = input.length; i < len; i++) { |
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var byte = input[i]; |
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crc = TABLE[(crc ^ byte) & 0xff] ^ (crc >>> 8); |
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} |
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return crc ^ -1; |
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}; |
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module.exports = exports;
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